[Spce-user] SBC outbound_proxy setting

[Barry Flanagan]

On 21 January 2014 19:13, Schaefer, Larry <Larry.Schaefer at pgi.com> wrote:

>  I am trying to add SPCE with SBC application into an existing SIP
> architecture, seeing if I could replace an existing SBC with SPEC SBC.
>
>
>
> I have questions about the outbound_proxy setting and how it handles
> failures.  The following A record points to four IP addresses, but in my
> architecture, I might expect only a couple of the IP addresses to respond
> (service is running in Amazon EC2, so servers might come and go).
>

Having an A record with 4 IP addresses doesn't really do what you want.
Only a single IP address will be returned by DNS, just that it will change
each time to return one of the 4 available. SPCE is still going to fail if
the IP is is given is not available.

>
>
> outbound_proxy=sip:blob.dev.us-west-1.bobdev.pgi.com
>

I am not totally sure of how outbound_proxy operates, so will leave that
for others.


>
>
> I have also attempted to create a service locator SVR DNS address (_sip._
> udp.blob.dev.us-west-1.bobdev.pgi.com), and SBC uses that address, but
> also does not attempt next server if the selected server does not respond.
>
>
I would think that SRV records would be the way to go for you. However, the
way you have set it up still results in only one of your 4 IPs being
returned, and again, gives you no redundancy.

What you need to do is to give each of your IPs a hostname in DNS and
remove the A records you have for them in blob.dev.us-west-1.bobdev.pgi.com,
and then set up SRV records for
_sip._udp.blob.dev.us-west-1.bobdev.pgi.comfor each of the 4 hostnames
giving them all the same weight and priority.

Now when SPCE queries it will receive back 4 possible endpoints for SIP
UDP, all with the same weight/priority and should try them all until it
gets a response (assuming that outbound_proxy/SPCE is set to use DNS SRV
lookups).

Have a look at http://en.wikipedia.org/wiki/SRV_record<http://en.wikipedia.org/wiki/SRV_record#Retrieving_a_SRV_record>
under
the section "Provisioning for high service availability"

Hope this helps.

-Barry Flanagan
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